The invention disclosed herein relates generally to systems for controlling the operation of equipment which regulates temperature in an air conditioned space, and more particularly to a control system for temperature regulating equipment including mechanical cooling equipment and an economizer for admitting outside air under suitable conditions.
It is well known in systems for regulating the temperature in an air conditioned space to use outside air to assist in maintaining the desired space air temperature when the outdoor air conditions are suitable for that purpose. Suitability of the outside air depends on its enthalpy which is a function of both its temperature and humidity. Outside air is typically brought into the air conditioned space through economizer equipment.
In general, a conventional economizer is set to operate at a control point temperature which has a predetermined relationship with the set point temperature of associated mechanical cooling equipment. Accordingly, the economizer control point may be a fixed number of degrees below the mechanical cooling set point, or it may be determined in accordance with a particular relationship with the mechanical cooling set point.
Conventional economizer equipment provides significant economic benefits in many space cooling applications. However, it lacks flexibility in some situations. For example, it may be desired to maximize economy of operation by operating mechanical cooling equipment only when a relatively high space temperature is reached. At the same time, it may be desired to have the comfort benefits of suitable outside air at the lowest temperature any benefit can be realized therefrom, even though there may be a variable range of temperatures below the mechanical cooling set point in which the economizer is not capable of maintaining a control point temperature.
The applicant has devised a control system and operating method for a temperature regulating system including mechanical cooling equipment and an economizer which offers substantial flexibility in the operation. Among other things, the applicant's system and method permits control of an economizer substantially independently of control of associated mechanical cooling equipment.